and normalizing 
B (an iL ~ 4 ‘bu = N 
sin( > (cosa cosa, )) sin + (cos8 COS8, )) 
a foil 
<n (cosa- cosa) =, (cos8- cosBo ) 
sin( “(cos y- COSY 5 )) 
._ >= (14) 
<1(cos8-cos®, ) 
If c>0 in equation (14), the equation for a rectangular area 
is obtained, i.e., equation (13). 
(d) Circular Array (fig. 10) 
The directivity function for a circular array, obtained from 
the generalized directivity function,is 
Se 
R= | 2G. y){ expj4[x(cosa-cosa, )+ (cos8-cos8, ) 
S25), 
+o (x,y (cosy(x,y)-1)] tds 
where s denotes arc length. 
IG 5 Ue ) 
V(x, y) 
OG 
Figure 10. Source and a circular ring. 
29 
